Publicly expose `shutil.ReadError` and `shutil.RegistryError`

Bug report

Bug description

shutil.ReadError and shutil.RegistryError are not included in shutil.__all__, making them inaccessible via wildcard import. Both exceptions are actively raised by public API functions:

• ReadError is raised by unpack_archive()
• RegistryError is raised by register_unpack_format()

The other shutil exceptions (Error, SameFileError, SpecialFileError) are all in __all__.

>>> from shutil import *
>>> try:
...     unpack_archive("nonexistent.zip")
... except ReadError:
...     pass
...
NameError: name 'ReadError' is not defined. Did you mean: 'KeyError'?

Impact

• from shutil import * does not export ReadError or RegistryError, so users cannot catch exceptions raised by unpack_archive() or register_unpack_format() without explicitly importing them by name.
• Neither exception is documented in Doc/library/shutil.rst, while the other three shutil exceptions (Error, SameFileError, SpecialFileError) all have dedicated .. exception:: entries.
• Tools that rely on __all__ for API discovery (linters, IDE autocompletion, documentation generators) will not surface these exceptions.

This was introduced in commit 6ac91723bd7 (bpo-8295, 2010) which added the archive functions and exceptions but did not add ReadError or RegistryError to __all__. A later fix for incomplete __all__ (#66855, 2014) added SameFileError but missed these two.

Verified on Python 3.14.3 in a clean venv.

Proposed fix

Add "ReadError" and "RegistryError" to __all__ in Lib/shutil.py, and add .. exception:: entries in Doc/library/shutil.rst to document them alongside the other exceptions.

CPython versions tested on:

3.14

Operating system:

All

Linked PRs

• gh-148004

Inspect all in Lib/shutil.py and the exception entries in Doc/library/shutil.rst, then review linked PR gh-148004 before starting. Verify that both exceptions are exposed by wildcard import and documented alongside the other shutil exceptions.